Method of manufacturing an enclosed transceiver

ABSTRACT

The present invention teaches a method of manufacturing an enclosed transceiver, such as a radio frequency identification (“RFID”) tag. Structurally, in one embodiment, the tag comprises an integrated circuit (IC) chip, and an RF antenna mounted on a thin film substrate powered by a thin film battery. A variety of antenna geometries are compatible with the above tag construction. These include monopole antennas, dipole antennas, dual dipole antennas, a combination of dipole and loop antennas. Further, in another embodiment, the antennas are positioned either within the plane of the thin film battery or superjacent to the thin film battery.

CROSS-REFERENCE TO RELATED APPLICATION

This patent application is a divisional of Ser. No. 09/115,492 filedJul. 14, 1998, now U.S. Pat. No. 6,045,652; which is a divisional ofapplication Ser. No. 08/947,681 filed Sep. 26, 1997, now U.S. Pat. No.5,779,839; which is a continuation of application Ser. No. 08/602,686filed Feb. 16, 1996, now abandoned; which is a continuation ofapplication Ser. No. 08/137,677 filed Oct. 14, 1993, now abandoned;which is a continuation in part of application Ser. No. 07/899,777 filedJun. 17, 1992, now abandoned. This patent application also is acontinuation in part of application Ser. No. 08/908,134 filed Aug. 6,1997 now U.S. Pat. No. 6,078,791; which is a continuation of applicationSer. No. 08/489,185 filed Jun. 9, 1995, now abandoned; which is acontinuation of application Ser. No. 08/123,030 filed Sep. 14, 1993, nowU.S. Pat. No. 5,448,110 which is a continuation-in-part of applicationSer. No. 07/899,777 filed Jun. 17, 1992, now abandoned.

TECHNICAL FIELD

The present invention relates generally to a process for manufacturingan enclosed transceiver, such as a radio frequency identification(“RFID”) tag.

BACKGROUND

In the field of radio frequency identification. (“RFID”), communicationsystems have been developed utilizing relatively large packages whosesize is on the order of that of a cigarette package or a substantialfraction thereof, and generally speaking, have been fabricated usinghybrid circuit fabrication techniques. These relatively large electronicpackages have been affixed, for example, to railroad cars to reflect RFsignals in order to monitor the location and movement of such cars.

With respect to an enclosed electronic apparatus, a system for handlingbaggage in an airport terminal is a typical application. Such a systemincorporates radio frequency identification (RFID) between interrogatorsand transceivers. Further, each baggage tag is an enclosed, batteryoperated transceiver.

Other smaller passive RFID packages have been developed for applicationsin the field of transportation, including the tracking of automobiles.These packages include reflective systems of the type produced by AmtechInc. of Dallas, Tex. However, these reflective passive RFID packageswhich operate by modulating the impedance of an antenna are inefficientin operation, require large amounts of power to operate, and have alimited data handling capability.

In still other applications of article location and tracking, such as inthe postal service or in the field of airline baggage handling andtransport, it has not been practical or feasible to use the aboverelatively large and expensive RFID hybrid packages on smaller articlesof transport such as letters, boxed mail shipments or airline luggage.Accordingly, in these latter areas of transport monitoring, as well asmany other areas such as inventory control of stored articles, articlelocation and tracking methods have traditionally employed bar codeidentification and optical character recognition (OCR) techniques whichare well known in the art.

Bar code identification and OCR techniques are labor intensive and may,for example, require several airline employees or postal workers tophysically manipulate the article and/or the bar code readers to readthese bar codes before the transported article reaches its finaldestination. In addition, the cost of bar code readers and opticalcharacter readers is high, limiting the number of locations at whichthese readers can be used. Furthermore, both bar code readers andoptical character readers tend to be highly unreliable.

In yet further and somewhat unrelated fields of: (1) animal tracking and(2) plant tracking, other types of passive RFID tags have been developedby Hughes/IDI/Destron of Irvine, Calif. These tags utilize a coilwrapped around a ferrite core. Such passive RFID tags have a verylimited range, on the order of nine (9) inches, have a very limited datahandling capability, and are not field programmable. In addition, thesetags are limited in data storage capacity and are slow in operation.

In view of the problems described above and related problems thatconsequently become apparent to those skilled in the applicable arts,the need remains for enclosed electronic apparatus includingtransceivers wherein the enclosure is inexpensive, readily manufacturedin high volume, appropriate in size for use as a stamp, label, or tag,and, in the case of transceivers, operable over distances of severalhundred feet without regard for the spacial orientation of theenclosure.

SUMMARY

The general purpose and principal object of the present invention is toprovide a novel alternative approach to all of the above prior art RFID,OCR, and bar code type location tracking and data storage systems. Thisnew approach as described and claimed herein represents a fundamentalbreakthrough in the field of article transport control in a wide varietyof fields, of which the fields of airline baggage transport, delivery ofparcels and mail, and inventory control are only three examples.

To accomplish this purpose and object, we have invented and developed anew and improved radio frequency identification device, an associatedelectrical system, and a method for communicating with a remote RFIDdevice from a local interrogator and controller. The size of this newdevice will typically be on the order of one inch square and 0.03 inchesthick, or only slightly larger and slightly thicker than a postagestamp. This device includes, in combination, an integrated circuit (IC)which is mounted in an approximately one inch square package and isencapsulated, for example laminated, in a flexible or rigid thin filmmaterial. This material may also include a suitable adhesive backing forreliably securing the package to an outer surface or printed label of anarticle of interest. The IC includes therein a receiver section fordriving suitable control logic and memory for decoding and storing inputinformation such as an identification number, the baggage owner's name,point of origin, weight, size, route, destination, and the like. Thismemory includes, but is not limited to, PROMS, EPROMs, EEPROMs, SRAMs,DRAMs, and ferroelectric memory devices. The IC also includes atransmitter section therein operative for transmitting this informationto an interrogator upon subsequent IC interrogation. An RF antenna isplaced in a desired geometrical configuration (for example, monopole,dipole, loop, bow-tie, or dual-dipole) and incorporated within or on thethin film material and adjacent to the IC in an essentially twodimensional structure, neglecting the approximately 30 mil thicknessdimension of the completed structure.

Advantageously, a thin battery is connected to the IC for providingpower to the IC. The IC also incorporates circuitry to allow foroperation in a sleep mode during transit and in storage in order toconserve power. Thus, at shipment points of origin, destination, andlocations in transit, an operator may encode data into the IC orinterrogate the IC by signaling the IC from a remote location to thereby“wake up” the IC without engaging in any hands-on operation.

In a preferred embodiment of the invention, the integrated circuitreceiver and transmitter are operated in a spread spectrum mode and inthe frequency range of 200 Mhz to 10 GHz, with the range of 800 MHz to 8GHz being the range of most importance. This operation has the effect ofavoiding errors or improper operation due to extraneous signal sourcesand other sources of interference, multipathing, and reflected radiationfrom the surrounding environment.

Accordingly, it is a further object of this invention to provide an RPIDelectronic device of the type described and method of fabricating suchdevice.

Another object of this invention is to provide an RFID system and methodof operation of the type described which utilizes RF transmitting andreceiving sections on a single IC. Such a system has applications fortracking people or articles in both storage and transit.

Another object of this invention is to provide an electronic device ofthe type described which does not include bulky hybrid circuits, usemodulation techniques described above for passive RFID tags, nor requirescanning of bar codes, bar code readers, optical character readers, orespecially clean operating environments.

Another object of this invention is to provide an electronic device ofthe type described which may be manufactured using integrated circuitfabrication and packaging processes.

Another object of this invention is to provide an electronic device ofthe type described which may be reliably and economically manufacturedat high yields and at a high performance to price figure of merit.

Another object of this invention is to provide an RFID device of thetype described which is field writable and has a transmission rangegreater than five (5) feet.

Another object of this invention is to provide a novel assembly processfor manufacturing the RFID electronic device described herein.

Another object is to provide a manufacturing process of the typedescribed which is conducive to high speed automation.

Another object is to provide an enclosed electronic device of the typedescribed which is further conducive to high speed product usage, sincethese RFID devices may be supplied to the customer in a tape and reelformat, a fan fold format, or a sheet format.

Another object of this invention is to provide an RFID device of thetype described which may be powered with the use of an RP coil andcapacitor and without the use of a battery. Such device is also referredto herein as the “passive” device embodiment. However, the term“passives” refers only to the fact that no battery is used, whereas theelectrical circuitry on the IC is indeed active while being powered bythe RF coil and capacitor combination.

Another object of this invention is to provide a non-contact method ofobject and person detection and location which can serve as areplacement for metal-to-metal contact in smart card applications and asa replacement for magnetic strip, bar code, and other types ofcontact-powered electronics. This novel method of object detection andlocation represents a significant saving of time and manual effort. Forexample, consider the time and effort involved when a person must firstremove a smart card from a pocket or billfold and then insert the cardin a card reader device before being allowed entry into a secured areawithin a building.

Another object of this invention is to provide an electronic device,system, and communication method of the type described which represents,in novel combination, a fundamental breakthrough in many diverse fieldsof article shipment, including the parcel post and postal fields, theairline industry, inventory control for many manufacturing industries,security, waste management, personnel, and the like.

Accordingly, an enclosed electrical assembly of the present inventionincludes: a rigid or flexible thin film support member having anintegrated circuit (IC) disposed thereon and an antenna incorporatedwithin the IC or positioned adjacent to the IC within a predeterminedarea of the thin support member; means on the IC for receiving andencoding data relating to the article being stored or shipped; and meanson the IC for reading the stored data and transmitting this data to anoperator at a remote location.

According to a first aspect of such an assembly, a base member and acover member each having conductive patterns developed thereon connectthe IC in series with two thin film batteries. By arranging twobatteries with the IC, no substantial current flows through a laminatedor folded portion of the assembly. Smaller signal levels, lower poweroperation, and longer useful life of the assembly results.

According to another aspect, antenna coupling is also provided to the ICwithout current flow through a laminated or folded portion of theassembly. Greater sensitivity in receiving and lower losses intransmitting result.

According to another aspect of the present invention, an RFID device hastwo modes of operation are provided with a wake-up circuit. The wake-upcircuit senses in-band energy and switches from a sleep mode to anoperating (waked) mode. The sleep mode being used during transit andstorage of the RFID device to conserve battery power.

According to another aspect of such an RFID device, the IC includesreceiver and transmitter sections characterized by spread spectrummodulation. Use of spread spectrum modulation reduces data transmissionand reception errors, reduces the possibility of improper operation inresponse to extraneous signal sources, reflected radiation from asurrounding noisy environment, and other interference. Battery power isthereby conserved.

According to another aspect of the present invention, the enclosureincludes an adhesive on an outer surface thereof. The adhesive permitsreliable and convenient securing of a device of the present invention toan article being transported or stored.

According to yet another aspect of the present invention, by enclosing atransceiver in film, an extremely light weight, durable, and thinpackage results. Such a package is appropriate for use in replacement ofor in conjunction with the conventional handwritten label, conventionalhand-cancelled or postage-metered stamp, and the conventional baggagetag.

According to another aspect of the present invention, the frequencies ofradio communication, modulation scheme, geometry of the antenna,capacity of the battery, and electrical properties of the enclosurecooperate for omnidirectional communication between an enclosedtransceiver of the present invention and a distant interrogator. Nomanual manipulation of the interrogator or transceiver is required forarea-wide communication such as confirming the contents of a deliveryvehicle or verifying inventory in place, to name a few examples.

According to an aspect of another embodiment of the present invention, aplurality of transceivers are enclosed and laminated between a pair offilms. One side of one of the films has adhesive capability. Thetransceivers are separated and arranged on a backing. A roll or tape ofthe backing having transceivers removably attached thereto is enclosedin an RF tight dispenser. The dispenser provide convenient access tounprogrammed transceivers for use on articles to be shipped. Whenremoved from the dispenser, a transceiver communicates with aninterrogator in the area for establishing transceiver identity, shippingauthorization, destination or storage criteria, date of issue, andsimilar information. By shielding transceivers within the dispenser fromwake-up signals, battery power is conserved.

These and other embodiments, aspects, advantages, and features of thepresent invention will be set forth in part in the description whichfollows, and in part will become apparent to those skilled in the art byreference to the following description of the invention and referenceddrawings or by practice of the invention. The aspects, advantages, andfeatures of the invention are realized and attained by means of theinstrumentalities, procedures, and combinations particularly pointed outin the appended claim.

DESCRIPTION OF THE DRAWINGS

FIG. 1A and FIG. 1B are functional block diagrams of enclosedtransceivers of the present invention.

FIG. 2 is a perspective view of an enclosed transceiver as shown in FIG.1A.

FIG. 3 is a plan view showing the conductive patterns on the base andcover members used in FIG. 2, including dotted line outlines of thelocations for the IC and batteries.

FIG. 4A through FIG. 4D are cross sectional views taken along lines 4—4of FIG. 3 showing four processing steps used in constructing theenclosed transceiver shown in FIG. 3.

FIG. 5A is a perspective view of an alternate embodiment of theinvention wherein the IC is mounted on a parallel plate capacitor whichin turn is mounted on a battery.

FIG. 5B is an enlarged portion of FIG. 5A.

FIG. 6A through FIG. 6E are cross sectional views taken along lines 6—6of FIG. 5 showing five processing steps used in constructing theembodiment shown in FIG. 5.

FIG. 7 is a cross-sectional view showing an arrangement of battery andcapacitor alternate to the embodiment shown in FIG. 5.

FIG. 8 is a perspective view of another alternate embodiment of thepresent invention having battery surfaces defining and performing thefunction of a bow-tie antenna.

FIG. 9 shows an alternate, passive device embodiment of the presentinvention in partially cut-away perspective view wherein the battery hasbeen altogether eliminated and further wherein a capacitor isperiodically charged from an external source in a manner described belowto provide operating power to the IC.

FIG. 10 is a top view of a web of enclosed transceivers of the presentinvention.

FIG. 11 is an exploded perspective view of the top and bottom films usedto construct one of the enclosed transceivers shown in FIG. 10.

FIG. 12 is a cross-sectional view taken along lines 12—12 of FIG. 11showing a portion of the web shown in FIG. 10 and illustratingelectrical coupling to and between the films.

FIG. 13A is a process flow diagram showing the steps of the presentinvention used to manufacture an enclosed transceiver.

FIG. 13B is a process flow diagram showing the steps of the presentinvention used to manufacture another enclosed transceiver.

FIG. 14 is a perspective view of a shielded cache for dispensingtransceiver devices on a sheet.

FIG. 15 is an X-ray view of the cache of FIG. 14.

In each functional block diagram, a single line between functionalblocks represents one or more signals. A person of ordinary skill in theart will recognize that portions of the perspective views andcross-sectional views are enlarged for clarity.

DESCRIPTION

FIG. 1A and FIG. 1B are functional block diagrams of enclosedtransceivers of the present invention. Enclosed transceiver 1 includes apair of batteries 2 and 3, a dipole antenna 4 and 5, and an integratedcircuit (IC) 11. Batteries 2 and 3 are in series connection through line6 and cooperate as powering means for-supplying power to IC 11 throughlines 8 and 9. As will be discussed below, the series connection of twobatteries simplifies conductor patterns in the enclosure. IC 11 is afour terminal device operating as communicating means for transmittingand receiving radio signals. Dipole antenna 4 and 5 couples radiosignals between IC 11 and the communications medium which separatesenclosed transceiver 11 from an interrogator, not shown. Theinterrogator is located up to 400 feet from enclosed transceiver 11.

Integrated circuit 11 is a transceiver including wake-up circuit 12,receiver 13, transmitter 14, control logic 15, and memory 16. Each ofthese functional circuits receives power signals VCC and GND on lines 8and 9. When a received signal has substantial in-band energy as detectedby wake-up circuit 12, control logic 15 enables receiver 13 forreceiving and decoding a radio signal on antenna 4 and 5. Received datais provided by receiver 13 to control logic 15. Control logic 15 writesreceived data into memory 16. Control logic 15 also processes (i.e.decodes, tests, or edits) the received data with data stored in memory16 and determines whether a response transmission is appropriate and thecontent of such a response. If a response is appropriate, control logic15 reads transmit data from memory 16 and enables transmitter 14 forsending the transmit data as a second radio signal on antenna 4 and 5.Control logic 15 operates as a controller for reading data from andwriting data to memory 16. Antenna 4 and 5 matches the medium to thereceiver and to the transmitter for improved receiver sensitivity, andreduced transmission losses. Dipole antenna 4 and 5 has a toroidalantenna pattern with a null along the axis of the toroid.

FIG. 1B is a functional block diagram of an alternate enclosedtransceiver of the present invention. Like numbered elements correspondto elements already described with reference to FIG. 1A. Enclosedtransceiver 18 includes loop antenna 19, battery 20, and integratedcircuit 21. Loop antenna 19 provides near omnidirectional communicationcapability as will be discussed with reference to FIG. 11.

Battery 20 is connected to antenna line 22 to reduce the number ofterminals required to connect integrated circuit 21 into enclosedtransceiver 18 and to improve the omnidirectional nature of the antennapattern. A novel enclosure implements this connection to be discussedbelow. Integrated circuit 21 is a three terminal device providing thesame functions as integrated circuit 11 already described with referenceto FIG. 1A.

As an example of a data call-up operation, consider the eventssurrounding checking baggage or mailing a package. When an enclosedtransceiver of the present invention is placed on the outside surface ofa piece of luggage by the airlines or on a package for shipment by thepostal service, an airline agent or postal worker operates aninterrogator. The interrogator transmits information to receiver 13 viaan RF communication link concerning data such as the owner's name, an IDnumber, point of origin, weight, size, route, destination, amount ofpostage prepaid, billing information for debit, postage, handling, orstorage costs due, time stamp, and the like. This received data iscoupled to control logic 15 for processing, encoding, and storage inmemory 16. Stored data is made available for call, up by an interrogatorat one or more points along the shipment route.

For example, upon reaching a point of shipment destination, aninterrogator calls up stored data and uses it at the point ofdestination for insuring that the item of luggage or shipment is mostassuredly and efficiently put in the hands of the desired receiver atthe earliest possible time. Specifically, an interrogator at thedestination point sends interrogation signals to the enclosedtransceiver 1 where they are received by antenna 4 and 5 and firstprocessed by sleep/wake up circuit 12. Wake-up circuit 12 operates tobring integrated circuit 11 out of a “sleep” mode into a “waked” modewherein receiver 13 receives and decades signals to provide receiveddata to control logic 15.

With integrated circuit 11 now in “waked” mode, memory 16 is read bycontrol logic 15 to call-up transmit data, i.e. the above six pieces ofinformation relating to the shipped article. Control logic 15 thencouples the transmit data to transmitter 14 and enables transmitter 14for sending transmit data to the interrogator.

Receiver 13 and transmitter 14 preferably employ one of the well knownspread spectrum modulation techniques including for example: (1) directsequencing, (2) frequency hopping, (3) pulsed FM or chirped modulation,(4) time hopping, or (5) time-frequency hopping used with pulseamplitude modulation, simple amplitude modulation or binary phase shiftkeying.

The communication circuitry of an interrogator (not shown) is designedto conform to the modulation technique, message encoding, and modes ofoperation described for the enclosed tnansceivers of the presentinvention. Interrogator design is understood by those skilled in the artand, therefore, is not described herein.

FIG. 2 is a perspective view of an enclosed transceiver as shown in FIG.1A. Enclosed transceiver 1 includes a base support layer 30 upon whichan integrated circuit 32 is disposed on the near end of layer 30 andconnected to a dipole antenna consisting of a pair of conductive strips34 and 36 extending laterally from IC 32. These conductive strips 34 and36 will typically be screen printed on the upper surface of base supportlayer 30.

A pair of rectangularly shaped batteries 38 and 40 are positioned asshown adjacent to IC 32 and are also disposed on the upper surface ofbase support member 30. Rectangular batteries 38 and 40 are electricallyconnected in series to power IC 32 in a manner more particularlydescribed below. Assembly of enclosed transceiver 1 is completed by thefolding over of an outer or upper cover member 42 which is sealed to theexposed edge surface portions of the base member 30 to thereby providean hermetically sealed and completed package. When cover member 42 isfolded over onto base member 30, conductive strip 50 is attached tobatteries 38 and 40 using conductive epoxy. Conductive strip 50 providesmeans for coupling a pole of battery 38 to a pole of battery 40; thusaccomplishing the series electrical connection of batteries 38 and 40.Integrated circuit 32 has transmitter, memory, control logic, andreceiver stages therein and is powered by batteries 38 and 40 during thetransmission and reception of data to and from an interrogator toprovide the interrogator with the various above information andidentification parameters concerning the article, animal or person towhich the enclosed transceiver is attached.

FIG. 3 is a plan view showing the conductive patterns on the base andcover members used in FIG. 2, including dotted line outlines of thelocations for the IC and batteries. During the initial manufacturingstage for the enclosed transceiver, base 30 and cover 42 are joined atan intersecting line 44. Dipole antenna strips 34 and 36 are shownpositioned on each side of IC 32. Two conductive strips 46 and 48 serveto connect the bottoms of batteries 38 and 40 to IC 32. Conductive strip50 is provided on the upwardly facing inside surface of top cover 42, sothat, when cover 42 is folded at intersecting line 44, the outerboundary 52 of cover 42 is ready to be sealed with the outer boundary 54of base support member 30. Simultaneously, conductive strip 50 bonded bythe conductive epoxy to batteries 38 and 40, completes the serieselectrical connection used to connect batteries 38 and 40 in series witheach other and further in series circuit with integrated circuit 32through conductive strips 46 and 48.

FIG. 4A through FIG. 4D are cross sectional views taken along lines 4—4of FIG. 3 showing four processing steps used in constructing theenclosed transceiver shown in FIG. 3. FIG. 4A shows in cross sectionalview IC 32 bonded to base support member 30 by means of a spot or buttonof conductive epoxy material 56. Conductive strip 48 is shown in crosssection on the upper surface of base support member 30.

In FIG. 4B, battery 40 is aligned in place as indicated earlier in FIG.2 and has the right hand end thereof bonded and connected to the uppersurface of conductive strip 48 by means of a spot of conductive epoxyapplied to the upper surface of conductive strip 48, but not numbered inthis figure.

In FIG. 4C, a stiffener material 58 is applied as shown over the upperand side surfaces of IC 32. The stiffener material will preferably be aninsulating material such as “glob-top” epoxy to provide a desired degreeof stiffness to the package as completed. Next, a spot of conductiveepoxy is applied to each end of conductive strip 50, and then coverlayer material 42 with the conductive epoxy thereon is folded over ontobatteries 38 and 40 and base member 30 to cure and heat seal and, thus,complete and seal the package in the configuration shown in FIG. 4D.

FIG. 5A is a perspective view of an alternate embodiment of theinvention wherein the IC is mounted on a parallel plate capacitor whichin turn is mounted on a battery. FIG. 5B is an enlarged portion of FIG.5A. The enclosed transceiver shown includes the combination of battery60, capacitor 62, and IC 64. When inrush current requirements for IC 64exceed the capability of battery 60 to supply surge current, forexample, due to inductive coupling or battery structure, inrush currentis supplied by capacitor 62. The structure of battery 60 is in directcontact with the upper surface 66 of a base support member 68. Thestructure of parallel plate capacitor 62 is positioned intermediate tothe upper surface of the structure of battery 60 and the bottom surfaceof IC 64. In order to facilitate making electrical contacts to capacitor62 and battery 60, respectively, an exposed capacitor bottom plate area65 is provided on the left hand side of this structure and an exposedbattery bottom plate area 67 is provided on the right hand side of thebattery-capacitor-chip structure. A plurality of antenna lines 70, 72,74, and 76 form two dipole antennas connected to opposite corners of IC64 in a generally X-shaped configuration and extend as shown from IC 64to the four corners of the package. Upper polymer cover 77 is sealed inplace as shown to hermetically seal all of the previously identifiedelements of the package between base support member 68 and polymer cover77.

FIG. 6A through FIG. 6E are cross sectional views taken along lines 6—6of FIG. 5 showing five processing steps used in constructing theembodiment shown in FIG. 5. Base starting material includes a first orbase polymer layer 78, such as polyester or polyethylene, which islaminated with a relatively impermeable material such as metal film,PVDC, or silicon nitride. Base layer 78 is coated on the bottom surfacethereof with a suitable adhesive film 80 which will be used for thedevice adhesion during device usage. If the adhesive is sufficientlyimpermeable, the impermeable coating may be omitted. The batteryconnection and attachment are made on the upper surface of base layer 78using a spot of conductive epoxy. Conductive epoxy is also used atinterface 94 between battery 60 and capacitor 62 and interface 98between capacitor 62 and IC 64.

Referring now to FIG. 6B, a thin film battery consisting of parallelplates 84 and 86 is placed on base layer 78. Next, a capacitorcomprising parallel plates 90 and 92 is attached onto battery layer 84using a conductive epoxy. Bottom plate 92 of capacitor 62 is somewhatlarger in lateral extent than top capacitor plate 90 in order tofacilitate the necessary electrical connection of battery 60 andcapacitor 62 to integrated circuit 96. IC 96 corresponds to IC 64 inFIGS. 5A and 5B. IC 96 is then attached to top capacitor plate 90 with aconductive epoxy at interface 98, thereby providing an electricalconnection. The bottom surface of IC 96 is metallized to facilitate thisconnection. In an alternate and equivalent fabrication process, an epoxycure heat step or metallization anneal step is used to enhance thesealing between the various above stacked elements.

Referring now to FIG. 6C, prefabricated insulating layer 100 is now laidover the battery/capacitor/IC stack in the geometry shown. Layer 100includes openings 102, 104, 110, and 112 therein for receiving aconductive polymer material as will be described below in the followingstage of the process. Prefabricated holes 102, 104, 110, and 112 inlayer 100 are aligned, respectively, to the battery contact, to thecapacitor contact, and to the contacts on the top of IC 96. Layer 100 isthen sealed to base polymer layer 78 using, for example, a conventionalheating or adhesive step.

Referring now to FIG. 6D, a conductive polymer material 108 is depositedin openings 102 and 104 in the lower regions of layer 100 and extendedup into the upper openings 110 and 112 of layer 100 to make electricalcontact as indicated on the upper surface of IC 96. The shapedconductive epoxy material 108 may also be preformed utilizing a stampingtool or silk screening techniques and is applied as shown over the uppersurface of layer 100. Conductive epoxy material 108 forms the innermostregion of the antenna structure extending from IC 96 out in the dualdipole geometry as previously described with reference to FIGS. 5A and5B. However, the complete antenna geometry shown in FIG. 5A is outsidethe lateral bounds of the fragmented cross sectional views shown inFIGS. 6A through 6E. At this point in the process, an epoxy cure heatstep is optional.

Referring now to FIG. 5E, polymer insulating layer 114 is formed on theupper surface of layer 100 in the geometry shown and further extendsover the exposed upper surfaces of the conductive epoxy polymer antennamaterial 108. Layer 114 is then sealed to layer 100 using either heat oradhesive sealing. Layer 114 provides a final hermetic seal for thecompleted device shown in cross section in FIG. 6E.

FIG. 7 is a cross-sectional view showing an arrangement of battery andcapacitor alternate to the embodiment shown in FIG. 5. As shown in FIG.7, the battery and capacitor are mounted side-by-side under the IC. Theelectrical connection for battery 118 and capacitor 120 to integratedcircuit 96 is provided by positioning the battery 118 and capacitor 120in the co-planar configuration shown on the surface of base polymerlayer 78. The bottom plate of battery 118 is connected throughconductive epoxy layer 128 to the top surface of IC 96. The bottom plateof parallel plate capacitor 120 is connected through conductive epoxylayer 128 to the top surface of the IC 96. A small space 126 is providedas shown to electrically isolate battery 118 and capacitor 120. Inaddition, in this embodiment of the invention, conductive material 128is extended as shown between the left side opening 130 in the layer 100and a lower opening 132 in layer 100. In a manner similar to thatdescribed above with reference to FIGS. 6A through 6E, layer 114 is thenextended over the top surface of layer 100 in the geometry shown.Conductive polymer material 128 extends to connect the crossed antennastructure of FIG. 5 to IC 96 shown in FIG. 7.

FIG. 8 is a perspective view of another alternate embodiment of thepresent invention having battery surfaces defining and performing thefunction of a bow-tie antenna. IC 138 is centrally positioned as shownon the upper surface of base support member 140 and is electricallyconnected to two triangularly shaped batteries 142 and 144, alsodisposed on the upper surface of base support member 140. Batteries 142and 144 are connected in series with IC 138 when protective cover member146 is sealed over the top surfaces of the two batteries 142 and 144 andthe IC 138 using processing steps previously described.

In the embodiment of the invention shown in FIG. 8, the entire outersurfaces of the two batteries 142 and 144 serve as a “bow tie” antennastructure for the enclosed transceiver. At communication wavelengths,the top and bottom surfaces of batteries 142 and 144 are coupledtogether. Batteries 142 and 144 are connected in series with the IC 138to provide DC operating power therefor in a manner previously described.Moreover, the dual use of the batteries as power supplies and antennastructures minimizes the number of terminals required to connect IC 138into an enclosed transceiver.

FIG. 9 shows an alternate, passive device embodiment of the presentinvention in partially cat-away perspective view wherein the battery hasbeen altogether eliminated and further wherein a capacitor isperiodically charged from an external source in a manner described belowto provide operating power to the IC. This embodiment is known as thepassive or battery-less device embodiment, since it contains no batterytherein. Instead, operating power is provided by a capacitor structureidentified as component 148 located beneath IC 150. A charge oncapacitor 148 is maintained by conventional RF charging circuits (notshown) on IC 150 which are energized from a remote source.

The enclosed transceiver shown in FIG. 9 includes a first loop antenna152 for receiving RF charging signals for capacitor 148 and a dipoleantenna formed of conductive strips 154 and 156 for receiving andtransmitting data to and from IC 150. As in previous embodiments,capacitor 148 and IC 150 are positioned and hermetically sealed betweena base cover member 157 and a top cover member 158.

FIG. 10 is a top view of a web of enclosed transceivers of the presentinvention. Laminated sheet 200 includes 36 enclosed transceivers 210simultaneously manufactured in a plurality of cavities as alreadydescribed. Sheet 200 in a preferred embodiment includes 252 enclosedtransceivers, each approximately 1.5 inches square. Alternatively, sheet200 includes one folded film as illustrated in FIGS. 2, 3, and 4; threecoextensive films 114, 100, and 78 as illustrated in FIGS. 6 and 7; ortwo coextensive films as is apparent from FIGS. 8 and 9, and FIGS. 11and 12 to be discussed below. Sheet 200, in one embodiment is sectionedto obtain individual enclosed transceivers by interstitial cutting,perforation and tearing, or sheering; sectioning being simultaneous withor following the step of sealing each enclosed cavity by lamination,embossing, hot stamping or the like. Alternatively enclosed transceiversare manufactured in a continuous strip, for example, one enclosure.

After manufacturing has been completed, a large number of finisheddevices 210 or webs are stored on a take-up reel 700 supporting acorresponding large plurality of the devices. Advantageously, storage ona take-up reel not only makes the present process conducive to highspeed automated manufacturing, but in addition makes the processcompatible to high speed manual or automated product dispensing and use.Large numbers of enclosed transceivers may be supplied easily to a userin a conventional tape and reel format. The user can readily detach onedevice at a time for immediate attaching to an article. Alternatively,enclosed transceivers are manufactured and shipped in sheets and latersectioned by the customer.

In yet another embodiment, devices are cut from the tape or sheet fromwhich they were manufactured and then removably mounted on a backing.The backing in one embodiment is in tape format and in anotherequivalent embodiment is in sheet format. When mounted to a backing,enclosed transceivers are more effectively stored in a cache fordispensing individually. The cache 702 includes means for dispensing(i.e. separately providing a transceiver on demand) and shielding meansfor preventing signal reception by enclosed transceivers within thecache. If shielding were not included, a supply of transceivers locatedwithin communicating range of an interrogator would soon expend batterycapacity by processing signals including, for example, wake-up signals.Means for dispensing includes, for example, mechanical devices forfeeding a tape or sheet through an opening 704 and mechanical devicesfor separating shielding materials from a tape or sheet. The formerdispensing means, in one embodiment of the cache, cooperates withshielding across the opening including conductive rollers, separatingbrushes, separating fingers, and the like. The latter dispensing means,in another embodiment of the cache, cooperates with conductive backingmaterial 706, or conductive foam as a backing or cover layer arranged toshield the exposed edges of a roll containing transceivers.

FIG. 11 is an exploded perspective view of the top and bottom films usedto construct one of the enclosed transceivers shown in FIG. 10. Theembodiment shown corresponds to enclosed transceiver 18 shown in FIG.1B. Top film 214 includes area 222 for lamination onto the top surface(pole) of battery 20; strip 218 for loop antenna 19; and, contact area226. Each of these three features, in a preferred embodiment, is formedof conductive ink. In an alternate and equivalent embodiment, thesethree features are formed of conductive epoxy. Bottom film 230 includesarea 238 for lamination onto the bottom surface (pole) of battery 20;strip 234 for loop antenna 19; contact area 254; and contact points 242,246, and 250 for connecting integrated circuit 21 to the battery andantenna. Each of these six features, in a preferred embodiment, isformed of conductive ink, though conductive epoxy is equivalent.

Contact 246 is intentionally misaligned with respect to area 222 toprevent shorting battery 20. However, strips 218 and 234 are aligned tocoincide, as are contact areas 226 and 254, respectively. These stripsand contact areas when joined by lamination cooperate as means forcoupling power from battery 20 to IC 21 and, simultaneously, forelectrically matching IC 21 to the communications medium by forming loopantenna 19. Thus, contacts 242, 246, and 250 correspond respectively tolines 24, 23, and 22 shown in FIG. 1B.

Unlike the antenna pattern of the dipole antenna shown in FIGS. 1A, 2,3, and 9, there is no null in the antenna pattern for loop antenna 19,due in part to the conductive structure of battery 20 being connected toone side of loop antenna 19. The combined loop antenna and batterystructure is also preferred over the dipole in that the combinationprovides an antenna pattern that is less subject to variation over abroad range of frequencies.

FIG. 12 is a cross-sectional view taken along lines 12—12 of FIG. 11showing a portion of the web shown in FIG. 10 and illustratingelectrical coupling to and between the films. The completed assemblyincludes similarly numbered elements already discussed with reference toFIG. 11. IC 290 is prepared for assembly by forming conductive bumps 306and 314 to terminals on its lower surface. In a preferred embodiment,bumps are formed of conductive epoxy. In an alternate embodiment,metallic bumps, such as gold, are formed by conventional integratedcircuit processes. IC 290 as shown is in a “flip chip” packagingorientation having substantially all circuitry formed on the surfacefacing film 230. Prior to assembly, a puddle of conductive epoxy isapplied to contacts 250 and 242. IC 290 is then located atop contacts250 and 242 so that bumps 306 and 314 are surrounded within puddles 302and 310. The film is then heated to set all conductive epoxy includingpuddles 302 and 310, as well as strips and areas including the antennaand contact areas 226 and 254, formed of conductive epoxy. Finally, topfilm 214 is aligned over bottom film 230 so that contact areas 226 and254 are pressed together.

FIG. 13A is a process flow diagram showing the steps of the presentinvention used to manufacture an enclosed transceiver of the type shownin FIGS. 10-12. The manufacturing process begins with a polyester filmused for the bottom and for the top. Material for the bottom in a firstembodiment is identical to the top and includes film with dimensionalstability, for example, polyester film that has been heat stabilized orpre-shrunk. These materials, though inexpensive, are porous tosubstances that degrade the life and functions of the battery andintegrated circuit. This disadvantage is resolved in a preferredembodiment by coating the outer surfaces of the material used for thetop and bottom film with a barrier material.

In the first step 410, barrier material, such as a silicon nitridedeposit, is formed on the outer surface by sputtering, or by chemicalvapor deposition (CVD), preferably plasma enhanced CVD. The depositprovides a hermetic barrier to prevent water vapor and othercontaminants from affecting (e.g. oxidizing) battery and transceivercomponents. In a first embodiment the resulting thickness of the depositis from 400 to 10,000 angstroms. In another embodiment, where thindeposits are desirable, coating on both sides of the film prevents pinholes in each deposit from aligning in a way that defeats hermeticity.The thickness of the deposit and the manner of formation are designchoices based on the selection of materials for the film and thedeposit, as well as the system requirements for hermeticity over time.For example an alternate and equivalent embodiment uses other barriermaterials including silicon oxide and silicon nitride deposited at athickness of 100 to 400 angstroms. The barrier material is formed insuch an embodiment using one of the processes including evaporation,deposition, chemical vapor deposition, and plasma enhanced chemicalvapor deposition.

In another embodiment of the present invention, a nitride film issputtered on the outside portion of a top and bottom base support layer.Each base support layer preferably comprises a polymer material such asa polyester film that is laminated with a barrier layer material such aspolyethylene and/or polyvinylidenechloride (PVDC). Formation of thebarrier material deposit can be deferred until the enclosed transceiveris encapsulated, provided that environmental concerns such ascontamination, over heating, and changes in pressure are addressed.

In step 420, a laminate adhesive is applied to the inner surfaces of thetop and bottom films. The laminate adhesive is activated in a latermanufacturing step to cause the top and bottom layers to adhere.Preferably, the adhesive is tack free at room temperature and selectedto match laminating equipment heat and pressure capabilities. In apreferred embodiment, butyl acrylate is extruded onto the films to coverthe entire inside surface of each film. In another embodiment, theadhesive is screen printed for economy.

In step 430, conductors are screen printed onto the films. In apreferred embodiment, the conductors are formed on top of laminateadhesive. Areas such as grid conductors 222 and 238 shown in FIG. 11 forcontacting the battery are, consequently, interspersed with areas ofexposed laminate adhesive to provide a more durable enclosure. In thisembodiment, a polymer thick film ink is employed. High conductivity isprovided by such inks that include copper or silver constituents. Theink preferably provides a stable surface for electrical butt contactformations. A low oxidation rate at storage temperature is desirable,though oxidation could be minimal in a controlled manufacturingenvironment.

Printed circuits on the top layer are arranged to perform multiplefunctions when the top and bottom layers are joined. First, a conductoron the top layer completes series or parallel circuits for deviceshaving contacts in two planes. Conductor 50 in FIG. 2 is one example.Second, a conductor on the top layer completes an antenna structure forthe transceiver integrated circuit, as illustrated in FIG. 8. Third, asingle conductor in the top layer accomplishes both the first and secondfunctions. See, for example, the conductor in FIG. 11 identified asareas 226, 222, and 216.

In an alternate embodiment, conductors are formed in a subtractiveprocess, for example, chemical etching. By using a positive screen printprocess, energy and material are conserved. Printed circuit technologyis applied in another embodiment wherein the step of attaching theintegrated circuit and the battery to a base material includes solderingand brazing. The base material in such an embodiment is one of a widevariety of printed circuit materials including polyimide and glass-epoxymaterials.

In step 440, the top and bottom base support layers are cut from theroll or web to form sheets as illustrated in FIG. 10 to facilitate useof automated component placement machinery. Each sheet is attached, instep 450, to a carrier panel for compatibility with conveyor basedmanufacturing facilities. At step 460, a carrier with sheet attached isloaded into a magazine or placed onto a conveyor for automatedmanufacturing. Steps 440-460, in an alternate embodiment of themanufacturing process of the present invention, are omitted asunnecessary when continuous manufacturing from roll stock is desirable.

In step 470 those portions of conductors that are to make electricalcontact with the integrated circuit are prepared with a coating orpuddle of conductive epoxy. In a preferred embodiment, silver filledepoxy is employed that remains wet at room temperature until thermallycured. Application of the epoxy is by screen printing. In an alternateembodiment, epoxy is applied by dispensing.

In step 480, integrated circuit die are placed so that epoxy bumpspreviously formed on the integrated circuit enter the puddles formed instep seven. The arrangement of the integrated circuit face down an thebottom film is commonly referred to as “flip-chip” orientation. In analternate and equivalent embodiment, integrated circuits are also placedin contact puddles formed on the top, i.e. cover layer. All die on thesheet are placed and aligned in this step 480 prior to proceeding withsubsequent cure.

In step 490, a batch of panels is heated to set the epoxy applied instep seven. In an alternate embodiment, a conveyor based oven supportscontinuous curing. Curing temperature and duration are design choicesthat match the epoxy curing requirements. In a preferred embodiment,curing is performed at 150 degrees Celsius for 3 to 5 minutes. The cureis selected so as not to interfere with the characteristics of thelaminate adhesive applied in step 420.

In step 500, a encapsulation material, commonly called “glob top epoxy”is applied over the integrated circuit. Suitable nonconductive materialsinclude those providing a stiffening property to protect the integratedcircuit and the electrical connections thereto from mechanical damage.

In step 510, the encapsulating material is cured. In a preferredembodiment, the encapsulating material is cured with ultravioletradiation. An alternate and equivalent embodiment, employs a thermalcuring process. The ultraviolet cure is preferred for rapidmanufacturing. However, use of a thermal cure in step 510 may permit useof a partial thermal cure in step 490, late perfected by additionalthermal cure duration provided in step 510.

In step 520, the battery or batteries are aligned and placed an the basesupport film. In an embodiment including stacked battery cells,connection is made using conductive tape having adhesive on both sidesof the tape. Such tape commonly includes conductive particles in theadhesive.

In step 530, the top or cover film is aligned over the bottom or basefilm. In an embodiment including a folded film, the top film is foldedover the base film. In an alternate embodiment employing continuousmanufacturing from roll stock, the base film and top film are alignedfor continuous lamination.

In step 540, the top cover film is pressed onto the bottom base film andheat is applied to activate the adhesive applied in step 420. For butylacrylate adhesive a temperature of from 95 to 110 degrees Celsius ispreferred.

In applications where the transceiver is to be used in harshenvironments, the seal provided by automated lamination equipment may beincomplete or have weaknesses caused, for example, by insufficient heator pressure at a point in an area to be sealed. Enclosing components ofvarying thicknesses can result in air pockets surrounding suchcomponents that, if too near the periphery, can also lead to weaknessesand voids. In such applications, the preferred process includes step 550wherein the periphery of each transceiver on a sheet is subject to asecond application of heat and pressure for activating laminate adhesiveapplied in step 420. The additional heat and pressure in such alocalized periphery can deform the films to form minute bosses. Thus,the step is called embossing. The aspect of the effective application ofheat and pressure is more important than the extent of consequentialdeformation.

In an alternate embodiment, each enclosure is evacuated. Lamination forsuch an embodiment is conducted in an evacuated environment. Embossingin yet another embodiment is also conducted in an evacuated environment.

After step 540, the circuitry of the battery powered transceiver isactive by virtue of the completed circuits formed when the top coverlayer is aligned and butt contacts are formed with components and thebase layer. Functional tests of multiple or individual transceivers arenow feasible.

In step 560, transceivers are functionally tested. To preventinterference between tests of individual transceivers, a pair ofgrounded plates with surface features are placed on both sides of asheet of enclosed transceivers so that each transceiver operates insidea shielded cavity. The wavelength used for testing is selected such thatleakage through the thickness of the embossed seal is negligible. Platessimilar to the embossing die used in step 550 are used in oneembodiment. Each cavity includes an antenna for transmitting stimulussignals and for receiving response signals for measuring the quality ofeach transceiver. Measurements include, for example, receiversensitivity, transmitted spectrum, message handling capability,self-testing, and response timing.

In step 570, the sheet of tested transceivers is sheered in twodimensions to singulate or separate the transceivers from one another.In an alternate and equivalent embodiment, a backing material is appliedto one side of the sheet prior to singulation. Singulation for thisembodiment is accomplished by kiss cutting through the top and basefilms leaving the transceivers attached to the backing material.Transceivers, whether attached to the backing or loose are then sortedbased on the results of functional testing performed in step 560 andadditional testing as needed.

FIG. 13B is a process flow diagram showing the steps of the presentinvention used to manufacture another enclosed transceiver of the typesshown in FIGS. 2-9. This embodiment of the method of the presentinvention includes nine (9) processing steps or fabrication stages whichare used in the overall manufacturing process and in the construction ofan enclosed transceiver.

In one embodiment the nine steps are performed sequentially as follows.In step 610, a circuit pattern is initially formed on a base layermaterial. This base layer material is preferably a polymer such as apolyester film that is laminated with a barrier layer material such aspolyethylene and/or polyvinylidenechloride (PVDC). In step 612, thecircuit pattern is cured and a conductive epoxy material is applied. Instep 614 an integrated circuit chip is aligned onto the base layer. Instep 616, two (2) batteries are aligned onto the base layer. In analternate enclosed transceiver, the batteries are stacked vertically ineither a series or parallel electrical connection. In step 618, theepoxy applied in step 612 is cured. In step 620, a stiffener material isapplied. In step 622 epoxy is applied to the top surface of the batteryand then the top half of the base layer is folded over the bottom halfso that the top half forms the top cover. In step 624, the epoxymaterial applied in step 622 is cured. Finally, in step 626, the packageis sealed to complete manufacturing of the package.

Various modifications may be made in and to the above describedembodiments without departing from the spirit and scope of thisinvention. For example, various modifications and changes may be made inthe antenna configurations, battery arrangements (such as batterystacking), device materials, device fabrication steps, and thefunctional block diagrams without departing from the scope of thisinvention. The various off-chip components such as the antenna, battery,and capacitor are manufactured on-chip in alternate and equivalentembodiments. As a second example, the antenna in another alternate andequivalent embodiment is formed an the outer surface or within the outerfilm. In such an arrangement, coupling to the antenna is through thecapacitance of the outer film as a dielectric. When formed on theexterior, the material comprising the antenna also provides hermeticityto the film for protecting the enclosed transceiver. Accordingly, theseand equivalent structural modifications are within the scope of thefollowing appended claims.

As previously suggested, an enclosed transceiver used as an RFID devicehas utility directed to a wide variety of applications including, butnot limited to, airline baggage (luggage, freight, and mail); parcelpost (Federal Express and United Parcel Service); U.S. Mail;manufacturing; inventory; personnel security.

While the particular invention has been described with reference toillustrative embodiments, this description is not meant to be construedin a limiting sense. It is understood that although the presentinvention has been described in a preferred embodiment, variousmodifications of the illustrative embodiments, as well as additionalembodiments of the invention, will be apparent to persons skilled in theart, upon reference to this description without departing from thespirit of the invention, as recited in the claims appended hereto. It istherefore contemplated that the appended claims will cover any suchmodifications or embodiments as fall within the true scope of theinvention.

The words and phrases used in the claims are intended to be broadlyconstrued. A “sticker” refers generally to a label, tag, marker, stamp,identifier, packing slip, invoice, package seal, tape, band, clasp,medallion, emblem, shield, and escutcheon regardless of printed orhandwritten material thereon. Mechanical coupling of a “sticker” sodefined to an article, person, plant, or animal is not restricted toadhesive but is intended to broadly include all forms of fastening,tieing, and securing.

What is claimed is:
 1. A method of manufacturing a radio frequencyidentification (RFID) transceiver, comprising the steps of: providing asheet of polymer film having first and second halves separated by aboundary; mounting an RFID transceiver integrated circuit on the firsthalf of the sheet; and folding the sheet in half along the boundary sothat the first half of the sheet overlies the second half of the sheetwith the transceiver between the two halves.
 2. A method according toclaim 1, further comprising the steps of: mounting a first electricalcontact on the first half of the sheet; and mounting a second electricalcontact on the second half of the sheet; wherein the folding stepincludes aligning the first and second halves of the sheet so that thefirst contact and the second contact abut so as to be electricallyconnected.
 3. A method according to claim 1, further comprising the stepof: sealing together the first and second halves of the sheet along acontour which encircles the RFID transceiver integrated circuit.
 4. Aradio frequency identification (RFID) transceiver, comprising: a sheetof polymer film folded in half along a fold boundary, so that the sheethas first and second halves joined along the fold boundary; an RFIDtransceiver integrated circuit and a first electrical contact mounted onthe first half of the sheet; and a second electrical contact mounted onthe second half of the sheet; wherein the first contact and the secondcontact abut so as to be electrically connected.
 5. A method ofmanufacturing and storing a plurality of miniature radio frequencyidentification (RFID) transceivers, comprising the steps of: mounting aplurality of RFID transceivers on a flexible sheet; placing the sheetwithin an RF shielded dispensing enclosure which prevents RF signalsoutside the enclosure from being received by the transceivers within theenclosure; and providing an opening in the enclosure through whichselected ones of the transceivers can be removed while maintaining theRF shielding of any transceivers which are not removed.
 6. A methodaccording to claim 5, wherein the mounting step includes detachablymounting the transceivers to an electrically conductive sheet, wherebythe conductive sheet shields the transceivers from RF signals until thetransceivers are detached from the conductive sheet.
 7. A methodaccording to claim 5, wherein the placing step further includes rollingup the sheet and placing the rolled up sheet within the RF shieldeddispensing enclosure.
 8. Apparatus for storing and dispensing aplurality of miniature radio frequency identification (RFID)transceivers, comprising: a plurality of RFID transceivers mounted on aflexible sheet; and a dispenser enclosing the sheet, the dispenserhaving RF shielding to prevent RF signals outside the dispenser frombeing received by transceivers within the enclosure, and the dispenserhaving an opening through which selected ones of the transceivers can beremoved while maintaining the RF shielding of any transceivers which arenot removed.
 9. Apparatus according to claim 8, wherein the flexiblesheet is electrically conductive and the transceivers are mounted to thesheet detachably, whereby the sheet shields the transceivers from RFsignals until the transceivers are detached from the sheet.